Can any on pls explain why the answer is C. Thanks.
P1 and P2 are both prime. Determine p1
1. p2 - p1 = 2
2. (p2)^2 - (P1)^2 = 120
1.There are many primes with difference 2, e.g. 3 and 5, 5 and 7. Therefore, 1 in INSUFF.
2. There are only two primes that satisfy this equation and differ by 2.
In fact, I was not sure whether there were more than two primes that satisfied just (2). 120 is not much, and if we try to put some numbers, we will see that difference between p1^2 and p2^2 becomes larger and larger after 29 and 31. However, then I tried 11 and 1.
It is C.